I'd like to dry hop an APA in the primary once fermentation has subsided and I've hit my FG. After an extra rest in the primary with the hops, I'd transfer straight to a keg. I'm concerned that this means around 17 days on the yeast. I don't think this should be a problem but thought I'd ask. Has anyone followed a similar procedure and had problems with the finished beer?

I was thinking this might even be beneficial. I detected a bit of diacetyl in my last attempt and figured it was because I was impatient and racked to the keg too quickly.

17 days on the yeast will be fine. I'm going to rack my current batch (an IPA) to secondary this Saturday - it will have been in primary for 21 days, and dry-hopped for the last seven. Like you say, it's important to give the yeast enough time not just for fermenting, but also to clean up after themselves. I wouldn't primary for less than two weeks, and would be happy to leave it for twice that.